Allan broke one of golf's longest winning droughts when he drained a 20-foot birdie putt from the back of the 16th green en route to a stressful but joyous one-shot win over American Tag Ridings on Monday (AEDT).

"Funny story; I won the Australian Open in 2002 and it was my second year, four years after my first win," Allan said.

"And I told my girlfriend, now my wife, 'It won't be four years until I win again.'

"Unfortunately it's been 23 years. It's a big relief to get a win.

"Came close a couple of times on the PGA Tour. Didn't get over the line."

The 51-year-old's only other professional victory came at the 1998 German Open on the DP World Tour.

His reward is a $US300,000 ($A476,000) pay day after only making the field at Mission Hills Country Club when Steve Stricker withdrew last weekend with a bad back.

That is almost half of what Allan had earned in 27 events since joining the seniors tour last year.

Allan, who entered the day with a one-shot edge, made five birdies on the front nine on Sunday, but played the back nine in only even par for a round of 67.

His 15-under 201 total for the tournament was only one shot shy of the record.

 
 
 
 
 
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"The guys who win [on tour] are playing really well," Allan said.

"You saw Stephen Ames, Steve Alker, Steve Stricker - all the Steves - but some of the scores they shot were great. You're looking at genuinely good golf.

"So I knew I had to step it up a little bit this year, otherwise I was going to be doing the same thing, and the first few weeks weren't that good, so this was nice that it came together."

Ridings carded a 67 and finished the day where he started - one behind Allan.

American Steve Flesch (64), Spaniard Miguel Angel Jimenez (65) and New Zealand's Alker (67) tied for third at 13-under.